Gastric Juice Case Study

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Follow the fate of probiotic bacteria after exposure to simulated gastric juice Low pH is of the most important factor that controls the growth and stability of probiotic bacteria in fermented products. The influence of simulated gastric juice on the viability of L. acidophilus was shown in (Table 4).The probiotic bacteria retain their viability when exposed to pH 3.0 for 3 h at 37 ͦ C and are less viability when exposed to the pH 2.0 for the same time period and incubation temperature (37 ͦ C). The average viable cell counts of L. acidophilus reduced from 7.62 ± 0.62 log CFU /ml on time 0 (before incubation period) to 6.33 ± 0.57,4.33 ± 0.57 log CFU /ml after incubation period (1.30 and 3 h) at 37 ͦ C in pH 2.0, respectively.…show more content…
The survival of the digestive tract conditions is essential for the later effects of probiotics into the gastrointestinal tract (35). Around 2.5 L of gastric juice at a pH nearly 2.0 is excreted per day in the stomach, which result in the destruction greater part of microorganisms consumed (20).Therefore, resistance to human gastric transit is prerequisite selection criterion for probiotic, however, during the digestive process the pH raises to about 3.0 due to the existence of food. (36). Maragkoudakis et al. (37) showed that a good probiotic have to survive at pH 3.0. They found that pH of stomach in human being ranges from 1.0 during fasting, to 4.5 after meal, and food ingestion follows during 3.0 h. Ng et al. (10) referred that L. acidophilus strains were also able to resist other types of acid accumulation caused by S. thermophilus and L. delbrueckii ssp. bulgaricus. Our findings are in agreement with those found from previous similar studies ( 11,25, , 37) where Lactobacillus strains were capable to retain their viability when exposed to pH around 3.0 but displayed loss of viability at lower pH…show more content…
acidophilus revealed an effective pH homeostasis mechanism when exposed to acid stress. According to Theron and Leus (28), pH homeostasis is defined as the ability of an organism to maintain its cytoplasmic pH at a value close to neutrality despite changes in the external pH. Ng et al.(10 ) reported that L. acidophilus has several ways to respond acid stress .Some have high cytoplasmic buffering capacity (pH 3.72-3.73) that may enhance their stability and permit them to withstand greater changes in the intracellular pH under acidic conditions. Probiotic lactobacilli strains are exposed to extreme acid stress when they arrive at the gut where hydrochloric acid is existent .Corcoran et al.(38) referred that in cultures lacking a respiratory chain, the role of the F0F1-ATPase is to provide a mechanism for pH homeostasis in acidic conditions, and the role of the F0F1-ATPase in organisms devoid of a respiratory chain is to generate a proton motive force and consequently, contributes in moving protons out of cells .They found that F0F1-ATPase demands ATP for removal of H+ from the cell and subsequently, maintaining pH homeostasis and cell viability. They claimed that the accumulation of ATP is because of energy-generating factories, such as the glycolytic system. McDonald et al. (39) showed that since fermentative bacteria gain less energy from substrates than do respiratory bacteria, fermentative bacteria adapt to low pH through

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